Cara's oral opioid cuts osteoarthritis pain in a Phase II trial

Cara Therapeutics ($CARA) said an oral version of its intravenous opioid painkiller showed promise in a Phase II osteoarthritis study, clearing the way for further trials as the company targets a bevy of approvals.

In a Phase IIa trial, an oral formulation of Cara's CR845 charted a dose-dependent reduction in reported joint pain after two weeks, the company said, from 25% at the lowest dose to 34% at the highest. Half of the patients on the highest dose, 5 mg twice a day, reported at least a 30% reduction in pain, Cara said, and 59% of those patients didn't require rescue medication by the end of the study.

Cara said the study confirmed the safety and tolerability of oral CR845, and the company is now planning to enroll a larger Phase IIb trial for the tablet next year, looking to better flesh out its efficacy before moving into late-stage osteoarthritis development. The results sent Cara's shares up about 20% on Wednesday morning.

The company's lead program is an intravenous formulation of CR845, which began a Phase III trial this year to test how well it can treat acute pain following abdominal surgery. Cara is also developing the liquid version for chronic itching and pain related to hysterectomy and bunionectomy.

Most opioid treatments work by activating the central nervous system's mu opioid receptors, relieving pain but often finding their way into the brain and leading to unintended effects like euphoria. Cara's drug, by contrast, targets the kappa opioid receptors in the nerves outside the brain, a formulation that allows CR845 to provide pain relief without the abuse-encouraging effects of other products, according to the company.

Cara pulled off a $55 million IPO last year on the promise that CR845 could establish itself as an alternative to commonly used analgesics.

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